Nearly 100 million tons of polymers are produced annually through radical polymerization making it one of the most industrially important polymerization methodologies to date. Traditional routes of radical polymerization use initiators such as azobisisobutyronitrile (AIBN), where the radical is generated through thermal decomposition or photolysis, and is then able to initiate the polymerization. However, these methods require harsh conditions, such as, high temperature or ultra-violet (UV) irradiation. Furthermore, these methods generally produce polymers with ill-defined characteristics, including broad or multi-modal molecular weight distributions.
More recently, controlled radical polymerizations have been developed, including atom transfer radical polymerization (ATRP), nitroxide mediated polymerization (NMP), iodine-transfer polymerization (ITP), reversible addition-fragmentation transfer (RAFT) polymerization, telluride mediated polymerization (TERP), stibine-mediated polymerization (SMP), etc. to produce polymers with controlled molecular weights (MWs) and molecular weight distributions. In particular, ATRP has proven highly successful because it not only produce well-defined polymers, but the polymers have chain-end groups that are readily susceptible to further modifications. Nonetheless, these routes generally require harsh conditions and, more concerning, contaminate the final polymeric product with trace metal catalyst residues that ultimately inhibit the application potential of these materials in medicinal or electronic applications. There is a need to produce well-defined polymeric materials, with functionalizable chain-end groups, under mild conditions (i.e. low temperature, non-UV light source), while eliminating the use of metal catalysts that would contaminate the final polymeric product.